Saliva is the principle protective agent for the mouth and thus is of primary importance to oral health maintenance. Perturbations in the salivary secretory mechanism can consequently lead to serious oral health problems. The objective of this project is to study the membrane and cellular processes which underlie the phenomenon of salivary fluid secretion and thus to contribute to our understanding of the fluid secretory process in normal and diseased states. Because similar secretory mechanisms are thought to be common to a number of other exocrine glands, this information should be of rather broad applicability and interest. During the present reporting period our specific areas of focus were the following. (1) The regulation of the rat parotid acinar Na/H exchanger and Na/K/Cl cotransporter by secretagogues was studied in order to clarify the role of these transporters in the fluid secretory process. (2) Studies of the functional properties of salivary ducts, in particular their ion transport properties and their responses to various secretagogues, were continued using both microfluorometric methods and a recently devised ductal preparation procedure. (3) The mobilization of intracellular calcium in acini isolated from normal human labial glands in response to various secretagogues was characterized. (4) The response of the human salivary ductal cell line HSY to hypotonic shock was studied.